Electronic devices are attempted to be made as small as possible in order to make them easily transportable in pockets or handbags. This tendency is, however, controversial to the feasibility of the terminal, because the user interface, i.e. mainly the keyboard and the display, must be made so small that on the display screen, there is room for limited information only (or the information must be shown on the screen with unreasonably small characters), and the keys and the spaces between them are unreasonably small for the fingers of an adult user.
As a solution, there are suggested various folding terminals, such as a telescopic mobile phone in a prior art document EP 0 944 219, where the telescopic telephone comprises two parts (upper part and lower part) that are sliding in relation to each other. Electronic devices with clamshell mechanisms are also known from prior art (for example a document EP 1473842), where the clamshell mechanism is implemented by a housing and a flap attached by a hinge at the bottom edge of the housing.
There are, however, some disadvantages in the prior art solutions. The terminal with a clamshell mechanism has to be opened, always when used, by turning a flap around the hinge. In addition the hinge structure in the clamshell mechanism is exposed to a significant load. Moreover a display in a terminal with a sliding mechanism is typically mechanically unprotected. Furthermore the terminals with the aforementioned mechanism cannot be used in a conference call mode without in a separate support member. Still in a clamshell model there is need for two displays if the user wants to use the user interface without opening the electronic device.